Why do BigLaw lawyers work so many hours

This may be a dumb question, but I don't understand why law firms work their employees to death. If there's so much work to do, why don't they just snatch up some of the unemployed lawyers out there?

I guess things are different in the current economy, but why have law firms historically overworked their lawyers rather than just hire more people? Personally, I'd rather work 40 hours per week and make 80K than work 80 hours per week and make 160K. I'm sure others would disagree about that, but burnout seems to be a serious issue for lawyers.

The only reasons I can see for having fewer employees and overworking them are:-fewer bonuses to give out-less money spent on benefits like health insurance, office space, etc-you'd probably have to pay 2 lawyers 100K each to do the same work as one lawyer at 160K-fewer people fighting for a piece of the partnership pie?

Even if you take total burnout out of the equation, though, there must be diminishing returns after 50 or so hours.

All the reasons I mentioned above(except the partnership one) would be true in all other fields, so why is law so infamous for working people to death when other types of companies would just add staff?

I think I've seen on here that the crazy hours are more common at big firms. Do lawyers at smaller firms do more normal work weeks - like 40-50 hours per week?

Biglaw clients are CEOs and Investment bankers- groups of people that work long hours and expect help at any time of day or night.

Makes sense. It just seems crazy to work so many hours. I don't know how people do it. I can see it maybe in your 20's and after your kids are all grown, but I can't imagine enjoying life with a family when your job requires that many hours.

I understand your point that if, say, a specific case requires a finite amount of work, then staffing 20 associates on it instead of 10 should allow everybody to work half as hard. But in reality, with a good case (/deal) flow, the 20 would finish early but then just go to work on something else. Either way, if you're sending lawyers home early, you're throwing away money.

(Also, firms aren't economies of scale necessarily. The overhead for each new lawyer (beyond salary) is pretty significant. You want to hire some more people to make Nikes or whatever, great, stick them in a corner somewhere. But you want to hire some more biglaw associates, you're going to need to find them their own offices (in your swanky building) (cubicles are for paralegals), their own secretaries, their own gold-plated benefits packages, and so forth. All this stuff makes perfect sense if you can bill a guy out for $700k every year; not quite so much if he's generating half that.)

I understand your point that if, say, a specific case requires a finite amount of work, then staffing 20 associates on it instead of 10 should allow everybody to work half as hard. But in reality, with a good case (/deal) flow, the 20 would finish early but then just go to work on something else. Either way, if you're sending lawyers home early, you're wasting money.

(Also, firms aren't economies of scale necessarily. The overhead for each new lawyer (beyond salary) is pretty significant. You want to hire some more people to make Nikes or whatever, great, stick them in a corner somewhere. But you want to hire some more biglaw associates, you're going to need to find them their own offices (in your swanky building) (cubicles are for paralegals), their own secretaries, their own gold-plated benefits packages, and so forth. All this stuff makes perfect sense if you can bill a guy out for $700k every year; not quite so much if he's generating half that.)